The present invention relates to a device for welding foils, films or sheets in web or bag form, with welding dies at right angles to the conveying direction of the foil and movable relative to one another, as well as with a periodically heatable resistance heating element.
In the case of welding devices of this type, continuously provided foil webs, particularly tubes, are welded to form bags and/or the bags are sealed. The foil web or bag is conveyed until the point to be welded is located between the welding dies. The heating element is heated and the foil web is jammed between the welding dies. The heat of the heating element is transferred to the foil and leads to the heat sealing thereof. The heating element and the foil must then cool, so that the weld becomes solid and only then can a further transfer take place.
Limits are placed on any increase to the production rate of such devices as a result of the heating and cooling times. For the purpose of increasing the production rate, it is known (DE-OS No. 3,024,517) to provide two fixed, heatable welding dies and to arrange reciprocatable welding dies between them. Thus, whilst cooling is taking place at one welding location, a transfer process can take place in the other welding location.